Systems and methods for cooling a controller assembly

ABSTRACT

Apparatus and methods for cooling controller assemblies for electric utility vehicles are disclosed. Auxiliary implements powered by electric motors onboard a utility vehicle create airflow that is captured and directed to provide increased ambient airflow across heat sinks used to dissipate heat from heat generating components. Airflow across heated surfaces is further created by vehicle movement and vacuum pressure. Fins and other heat dissipating architecture are employed. Features of the cooling systems enable increased controller assembly functionality and/or decreased controller assembly package size.

CROSS REFERENCE

This application is a divisional and claims the benefit of U.S. patentapplication Ser. No. 12/825,122 filed Jun. 28, 2010, which claims thebenefit of U.S. Provisional Patent Application No. 61/220,907 filed onJun. 26, 2009. Both of these prior applications are incorporated byreference herein in their entirety.

TECHNICAL FIELD

This disclosure is generally related to utility vehicles, such as lawnand garden tractors and mowers, and more particularly to systems andmethods for cooling controller assemblies used to control electricmotors associated with such vehicles.

BACKGROUND OF THE INVENTION

Utility vehicles, such as, for example, lawn and garden tractors andmowers, have traditionally relied upon internal combustion engines asthe prime mover transferring power through mechanical linkages. However,electric drive utility vehicles have emerged as viable alternatives tointernal combustion utility vehicles, particularly due to rising oil andfuel prices. Such vehicles employ electric power supplies to providepower through controller assemblies to one or more electric motors thatmay be used to propel the vehicles and/or power auxiliary equipment,such as a cutting blade on a lawn tractor. These controller assembliesnot only act as energy conduits, but also incorporate logic to analyzevarious inputs and determine various outputs. All of these functionsgenerate heat, which must be dissipated to prevent damage to controllerassembly components. With the advancement of electric drive utilityvehicles and their functionality, demands on controller assembliescontinue to increase. As the controller assemblies handle more input andgenerate more output, they also generate more heat, which presentsproblems in the area of temperature control.

One solution to these problems is to increase the size of the controllerassembly. A larger controller assembly has a larger heat-absorbinghousing to act as a heat sink. In addition, a larger controller assemblyprovides more space for separating the various internal heat-generatingcomponents needed to provide the increasing levels of functionality.However, increasing the size of the controller assembly also increasesmaterial costs and consumes more vehicle package space. Thus, thechallenge is to maximize heat dissipation while maintaining a minimallysized, compact controller assembly design. This disclosure is directedto addressing this challenge, as well as others, in the general area ofcontroller assembly package and design.

SUMMARY OF THE INVENTION

The present invention comprises systems and methods for coolingelectronic control systems and controller assemblies used to controlelectric motors that propel a vehicle and/or perform auxiliaryfunctions, such as to turn mower blades. Various embodiments aredisclosed to illustrate how airflow created through use of auxiliarydevices and/or movement of the vehicle may be harnessed to improvedissipation of heat generated by a controller assembly. In addition,some embodiments efficiently place structural heat sinks designed toabsorb and conduct heat away from concentrated heat generation pointswithin the controller assembly, such as MOSFET transistors. The coolingsystems and methods described herein allow existing controllerassemblies to take on more functionality without increasing in size.Alternatively, the systems and methods may be utilized to reduce thesize of existing controller assemblies while maintaining present levelsof functionality without concerns of overheating, thus saving materialcost and package space on utility vehicles.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forth one ormore illustrative embodiments which are indicative of the various waysin which the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a utility vehicle employing a system forcooling a controller assembly according to a first embodiment of thepresent invention.

FIG. 2 is an exploded perspective view showing certain components of thefirst embodiment.

FIG. 3 is a partially sectioned view along the line 3-3 of FIG. 1.

FIG. 4 is a top plan view of a utility vehicle employing a system forcooling a controller assembly according to a second embodiment of thepresent invention.

FIG. 5 is an exploded perspective view showing certain components of thesecond embodiment.

FIG. 6 is a partially sectioned view along the line 6-6 of FIG. 4.

FIG. 7 is a perspective view of the second embodiment with certaincomponents removed for clarity.

FIG. 8 is a top plan view of a utility vehicle employing a system forcooling a controller assembly according to a third embodiment of thepresent invention.

FIG. 9 is a partially sectioned view along the line 9-9 of FIG. 8.

FIG. 10 is a partially sectioned view along the line 10-10 of FIG. 9.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the present invention in accordance with itsprinciples. This description is not provided to limit the invention tothe embodiments described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiments describedherein, but also other embodiments that may come to mind in accordancewith these principles. The scope of the present invention is intended tocover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers, such as, for example, in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. Such labeling and drawing practices do not necessarilyimplicate an underlying substantive purpose. As stated above, thepresent specification is intended to be taken as a whole and interpretedin accordance with the principles of the present invention as taughtherein and understood by one of ordinary skill in the art.

FIGS. 1-3 illustrate a first embodiment of the present invention, whichcomprises a controller assembly 105 designed and mounted in a manner soas to expose its heat conducting exterior to air currents generated byan auxiliary implement. While this embodiment is illustrated inassociation with a lawn tractor, it will be understood that theinvention could be adapted to work with other auxiliary equipment,wherein operation of the equipment generates an airflow. The auxiliaryequipment will have at least one primary work function, such as trimminggrass, digging a hole, or brushing off a sidewalk, however performanceof that primary work function will have the secondary effect ofgenerating an airflow.

FIG. 1 shows a top view of a utility vehicle 100, in this case a lawntractor having three rotating blades 175 suspended from a mowing deck180. The mowing deck 180 is, in turn, suspended from the frame 190 ofutility vehicle 100 by a set of chains or linkages (not shown). Theblades 175 are rotated, either directly as in the case of the centerblade or through a belt and pulley system 178 as in the case of the leftand right blades, by an electric auxiliary motor 176. The electricauxiliary motor 176 is controlled by controller assembly 105, which islocated in the illustrated embodiment at approximately the center ofvehicle 100. FIG. 1 also displays two electric drive motors 177, eachfor driving separate right and left wheels of utility vehicle 100. Forclarity, motors used to propel the vehicle are referred to herein asdrive motors and motors for powering utility equipment, such as mowingblades 175, are referred to herein as auxiliary motors. Utility vehiclesmay incorporate a single controller assembly to power both drive andauxiliary motors, may have separate controller assemblies for poweringthe drive motors and the auxiliary motors, or may even have separatecontroller assemblies for each of the individual motors on the utilityvehicle. Information regarding the internal construction of thecontroller assemblies, their various embodiments, and explanations as tohow they receive input and drive their associated electric motors isdisclosed in more detail in U.S. patent application Ser. Nos. 12/209,120and 12/367,144, the terms of which are incorporated herein by referencein their entirety.

As seen in FIG. 2, controller assembly 105 comprises a controllerhousing 110 having a plurality of outwardly extending fins forincreasing conductive surface area, and a thermal conducting base plate120, which also may be referred to herein as the “heat sink.” Thecontroller housing 110 and base plate 120 join to form a seal, with theaid of a sealing gasket 113, to protect the internal components ofcontroller assembly 105. On its top surface, controller housing 110provides a water-tight circular connector 114 for receiving a wiringharness (not shown) used to supply control inputs to and feedback fromcontroller assembly 105. The housing 110 also provides a terminal block116 having five terminals—three for driving the 3-phase auxiliary motor176 and two for creating a circuit for receiving power from an onboardpower supply (not shown). The controller housing 110 also provides fourbolt housings for receiving mounting bolts 112 used to secure it to baseplate 120. The size and shape of the controller housing, the quantityand placement of its fins, and the location, size and type of itsconnector and terminal block will vary across different embodiments. Forexample, alternative controller housings that might be substituted forcontroller housing 110 are illustrated in U.S. patent application Ser.No. 12/367,144.

In the illustrated embodiment, base plate 120 is a solid componenthaving a flat upper surface 122 for mating to controller housing 110 anda downwardly extending member 124 which fits through a cutaway 132provided in mowing deck 180. This is further illustrated in FIG. 3,where controller assembly 105 is shown in assembly position. As shown,the flat upper surface 122 extends beyond deck cutaway 132, providing aflange for mating controller assembly 105 to mowing deck 180. This maybe done using a set of rivets 102 as shown; however any known fastenerssufficient to maintain a rigid connection may be used. The controllerassembly 105 may be positioned anywhere on the upper surface of mowingdeck 180, but is preferably at a point at or near the centralleft-to-right axis of vehicle 100 such as shown in FIG. 1 so as tomaintain overall deck weight distribution. Additionally, placingcontroller assembly 105 aft of rotating blades 175 and associatedauxiliary motor 176 provides for increased protection from objects thevehicle 100 may encounter in its path. As shown in FIG. 3, controllerassembly 105 is also vertically separated from auxiliary motor 176,which is mounted atop belt drive housing 127. This further separation isbeneficial because auxiliary motor 176 is an additional source of heat.

The base plate 120 functions as the primary heat sink for controllerassembly 105, and thus is preferably formed from a good heat conductivematerial such as aluminum. By extending base plate 120 through deckcutaway 132, the primary heat sink of controller assembly 105 is exposedto the rapid airflow present under mowing deck 180. This rapid airflow,caused in the illustrated embodiment by rotation of rotating blades 175,cycles across heat sink 120 helping to convectively cool controllerassembly 105. As blades 175 rotate, warm air having circulated acrossbase plate extension 124 exits out of discharge chute 181. Thisdischarge and the turbulence caused by the blade rotation creates a lowpressure condition under the mowing deck 180, which in turn causes freshcooler air to be pulled in from under its edges. Thus, operation ofrotating blades 175 draws a continuous flow of ambient air under mowingdeck 180, around its underside (and thus across base plate extension124), and out discharge chute 181. The thicker the base plate extension124, the better it will serve as a heat sink. However, increasedthickness adds weight and material cost to vehicle 100 and may alsoreduce ground clearance. Thus, the thickness of the base plate extension124 may vary and is determined based on the cooling requirements andcost, weight and package constraints of a particular utility vehicle100.

Deck mounting, as provided in this embodiment, inevitably exposescontroller assembly 105 to a harsher environment than in cases where acontroller assembly is mounted upon or suspended from vehicle frame 190.Though certain precautions may be taken such as centralized placement asdiscussed above, it may be necessary to provide isolation so as toabsorb impact shocks and vibrations common to mowing decks in someenvironments. This could be done, for instance, by placing grommets inthe joints used to secure controller assembly 105 to mowing deck 180. Inaddition, connector 114 and terminal block 116 should be of a properspecification to endure increased levels of moisture and debris.

While the embodiment illustrated in FIGS. 1-3 displays controllerassembly 105 in connection with a series of rotating blades 175,application to other auxiliary devices that create airflow iscontemplated. For instance, an auxiliary motor 176 used to drive ablower creates a vacuum into which fresh air is pulled. That air couldbe directed across a controller assembly base plate in similar fashionas discussed above. Other auxiliary equipment that involves rotatingcomponents such as a tiller or spreader might also create airflows thatcould be similarly utilized for cooling purposes.

FIGS. 4-7 illustrate a second embodiment of the present invention. Thisembodiment incorporates a duct 230 which attaches to mowing deck 280 soas to create a channel 250 for directing air toward and across orthrough controller assembly 205 of utility vehicle 200. Though similarto controller assembly 105 of FIGS. 1-3, controller assembly 205includes a base plate 220 that has been inverted such that its extendingmember 224 protrudes upward into channel 250 created by duct 230 insteadof down through cutaway 232 in mowing deck 280. In fact, deck cutaway232, which can be seen in FIG. 6, is not essential for use withcontroller assembly 205. In some embodiments, there may be no cutaway inthe deck under the base plate. While having such a cutaway increases thebase plate's surface area exposed to ambient air, mowing deck 280 isideally metallic and can also transfer heat through to the ambient airbelow. Alternatively, where a deck cutaway 232 is present, it could beutilized by a base plate extending in both directions, such that a firstportion extends upward into channel 250 and a second portion extendsthrough deck cutaway 232, thereby combining concepts from the first andsecond embodiments.

In any case, base plate 220 provides a flange 223 used to securecontroller assembly 205 to mowing deck 280, and specifically controllerhousing 210 is secured to extending member 224 of base plate 220. Thismay be done, as shown in FIG. 5, with a series of mounting bolts 212which insert into threaded housings in base plate 220, or by any knownfastening means capable of providing a rigid connection andenvironmental seal. In this case, controller housing 210 of the secondembodiment is identical to controller housing 110 of the firstembodiment. However, other housing configurations could be substitutedas explained in association with the first embodiment.

As shown in FIGS. 5 and 6, base plate 220 also provides a series of airpassages 225. Though these air passages 225 may be of any number and maytake on any shape, ideally they lend to base plate manufacturability,maximize surface contact between base plate 220 and the ambient airpassing through it, and minimize constriction of air through the channel250 formed by the duct 230. The base plate 220 shown may be formed usinga variety of techniques such as casting, extruding or drilling. Materialremoved from such a process may be recycled to offset any additionalprocessing steps required to create the air passages 225. It will beunderstood with reference to FIG. 4 that the air passages 225 do notprovide the only path for air travelling through channel 250. As duct230 is wider than controller assembly 205, air traveling through channel250 may also travel around controller assembly 205. Accordingly, analternative embodiment might utilize a base plate with no internalpassages (such as air passages 225) as a means to save cost. However,this would reduce airflow rate and surface contact with the base plate,resulting in less efficient cooling.

FIG. 4 shows a top view of duct 230, which attaches to mowing deck 280just aft of auxiliary motor 276 and extends rearward past the entirecontroller assembly 205 and off the back edge of mowing deck 280. Amating flange 283 is formed along all but this trailing edge of duct 230for mating to mowing deck 280. mating flange 283 may be fastened tomowing deck 280 by any conventional means, but is shown affixed with aseries of rivets. Ideally duct 230 is formed with a series of pre-formedholes in mating flange 283 to facilitate its location on mowing deck280. As duct 230 primarily serves to direct air, it is ideallyconstructed of an easily formable, lightweight and inexpensive materialsuch as plastic; however any reasonable solid material could besupplemented.

As seen in FIG. 5, duct 230 provides a cutaway 233 in which controllerassembly 205 is disposed. The perimeter of cutaway 233 includes tabs 231which fit into grooves 226 formed in base plate 220. The grooves 226 areideally somewhat oversized to allow for component manufacturingvariability. The duct 230 is thus further located and held in place bycontroller assembly 205 when controller housing 210 is mated to baseplate 220 as shown in FIG. 6. Not only does this help locate and secureduct 230, it helps to prevent air passing through channel 250 fromescaping around the edges of controller assembly 205. It should be notedthat the connection between duct 230 and controller assembly 205 neednot be air tight. Some air bleed from channel 250 may occur withoutcompromising the function of the system. This embodiment preventscontroller housing 210 from being fixed to base plate 220 prior to thepoint of final assembly wherein duct 230 is mounted to mowing deck 280.However, controller housing 210 may be independently removed for serviceat any time.

FIG. 6 displays a partially sectioned side view of this embodimentshowing channel 250 created by duct 230. As indicated by the arrows, airenters channel 250 through a channel entrance opening 252, which islocated in the top of mowing deck 280 just aft of the leading edge ofduct 230. As discussed in accordance with the first embodiment, rotationof rotating blades 275 excites the air under mowing deck 280, creating alow pressure area which, combined with blade angle and orientation,tends to pull fresh air up from under the edges of mowing deck 280. Theblades 275 then cause the air to rotate around mowing deck 280 and exitthrough discharge chute 281. The channel entrance opening 252 providesan additional exit for the turbulent air. Airflow through the channelentrance opening 252 could be substantially increased by closing offdischarge chute 281, such as often done in mulching operations.

After the air enters channel 250, it passes through a screen assembly240 which filters out grass or other solid objects. The airflow thenproceeds through or around base plate 220, and finally exits off theback of mowing deck 280. Thus, duct 230 combines with the upper surfaceof mowing deck 280 to create channel 250 so as to direct a constant flowof pressurized air toward the primary heat sink (i.e., base plate 220)of controller assembly 205 to further increase heat dissipation throughair convection during operation of rotating blades 275.

To increase air intake into channel 250, other embodiments may provide aforward-facing air scoop (not shown) for collecting additional airflowbased on the forward motion of utility vehicle 200. Such a scoop couldeither be a separate component suspended from the underside of themowing deck, or may be formed in the mowing deck itself, for instance byextending the mowing deck surface forming the rear edge of channelentrance opening 252 down and raising the mowing deck surface formingthe leading edge of the channel entrance opening 252 up. This would havethe effect of causing the channel entrance opening 252 in FIG. 6 toappear tilted clockwise rather than flat as shown.

FIG. 7 illustrates a perspective view of controller assembly 205 andscreen assembly 240 referred to above, but with duct 230 removed forillustration purposes. Screen assembly 240 includes a screen 241 havinga plastic perimeter casing 242 and a handle 244 which is used to installand remove screen assembly 240 from a screen receptacle 246 fixed tomowing deck 280. The screen 241 is perforated so as to allow air to passthrough while stopping larger objects that might damage controllerassembly 205 or block channel 250. Ideally, screen 241 is a wire meshwith sufficient strength to resist damage from impact with small stonesor other debris that may be propelled against it. The mesh should befine enough to stop harmful debris, but coarse enough to avoidconstricting airflow through channel 250. The screen receptacle 246,which locates screen assembly 240 and holds it in position, is shaped tomatch the inside contour of duct 230 such that, when assembled, air isprevented from passing around it. Screen receptacle 246, which serves todirect all airflow through screen 241, is ideally formed of a rigidplastic and provides an attachment flange for connection to mowing deck280. Receptacle 246 may be secured to mowing deck 280 using any varietyof means, but is attached with four rivets as shown.

The screen receptacle 246 positions screen 241 such that it is angleddownward. This allows gravity to assist in clearing grass and otherdebris that may become pressed against it by the airflow. Nevertheless,screen assembly 240 will require occasional cleaning—especially whenworking in moist environments. To facilitate this, handle 244 isprovided to pull it out of screen receptacle 246 so that it may be wipedclean and replaced. To accommodate insertion and removal of screenassembly 240, duct 230 provides a screen slot 234 which aligns withscreen receptacle 246. The slot is covered by a clip-in fascia 235 whichfurther locates and secures screen assembly 240. The screen casing 242may be equipped with a tapered leading edge (not shown) so as to assistin assembly and reinsertion after cleaning.

To allow for easy cleaning or clearing of screen 241, screen receptacle246 may provide a stiff downward-facing edge (not shown) at its entrypoint that abuts the screen and scrapes against it as the screen isremoved. This scraping action will clear the screen in most cases. Thefascia 235 or duct 230 may also encompass a locking tab (not shown) toprevent the complete removal of screen assembly 240 from screenreceptacle 246 unless the tab is depressed. In such a manner, screen 241might be cleaned by an operator through a simple up and down pump ofhandle 244. High end models might employ a wiping mechanism (not shown)that automatically clears screen 241 when a lack of airflow is detectedin channel 250. Airflow could be measured by a variety of known meanssuch as placement of a Pitot tube within channel 250 beyond the screen.The Pitot tube (not shown) could be snap-fit into a hole in duct 230 andelectrically connected to the wiping mechanism.

As it may be desirable for an operator to completely remove a deckassembly or auxiliary implement housing for certain utility vehiclefunctions, controller assemblies directly mounted to such assemblies orhousings, such as those described in the previous embodiments, arelimited to powering the auxiliary motors associated therewith. Obviouslythe drive motor(s) of the utility vehicle must still be powered in theabsence of such an assembly or housing in order to propel the vehicle.Thus, in the above embodiments, a separate controller assembly (notshown), mounted to the frame of the utility vehicle itself, may be used.FIGS. 8-10 show a third embodiment which includes concepts used in thesecond embodiment, such as a duct connected to an auxiliary housing soas to create a channel, but applies them to a frame-mounted controllerassembly 305. Because controller assembly 305 is mounted to vehicleframe 354, it could potentially control both auxiliary motors 376 anddrive motors 377. Obviously controlling more motors generates more heat,thus the need for increased heat dissipation.

The utility vehicle 300 of FIG. 8 has a mowing deck 380 with tworotating blades 375, each directly powered by separate auxiliary motors376. Controller assembly 305 is suspended from vehicle frame 354 forwardof auxiliary motors 376, and centered from left to right across vehicle300. FIG. 9 demonstrates a side view of mowing deck 380, controllerassembly 305 and one of the auxiliary motors 376 (the other electricmotor 376, slightly aft and offset from the one shown, has been removedfor clarity). Finally, FIG. 10 shows a section view of controllerassembly 305 and vehicle frame 354 from the rear of vehicle 300.

As is quickly apparent with reference to these figures, controllerassembly 305 of this embodiment has been modified from those of thepreviously described embodiments. In addition to its reversedorientation, fins 318 have been relocated so as to extend downward fromcontroller assembly 305 and run in line with the air movement caused byforward motion of vehicle 300. As a result, connector 314 and terminalblock 316 have been relocated on different sides of controller housing310. The air passages 225 of base plate 220 have been replaced by airpassages 325, which are separated by ribs 329 in base plate 320. Theribs 329 are not closed in, but rather open on the side extending awayfrom controller assembly 305. Again, the base plate 320 is ideallyformed of aluminum, using known manufacturing means such as extrusion.The controller housing 310 provides four mounting bosses 311 forreceiving mounting bolts (not shown) to secure it to threadedreceptacles in base plate 320, though additional fasteners may be usedas needed to provide a rigid, sealed connection between the components.

As best shown in FIG. 10, vehicle frame 354 consists of a floor plate356 and frame rails 345, both of which are typically steel to providesufficient structure to vehicle 300. As floor plate 356 is directlyexposed to sunlight, it can often get quite hot. Thus, ideallycontroller assembly 305 is not mounted directly to floor plate 356 orframe rails 345, which receive heat from floor plate 356 throughconduction. Instead, an aluminum skin 347, coated in structural tape(not shown) fixes to the bottom of frame rails 345 and extends across aportion of vehicle 300 providing a cooler mounting surface forcontroller assembly 305. The base plate 320 is then attached to aluminumskin 347 by inserting any of several known fasteners such as rivetsthrough a plurality of mounting holes 328 along the sides of base plate320. A layer of insulation 348 fills the gap between aluminum skin 347and floor plate 356 so as to insulate controller assembly 305 from solarheat gain. To improve stiffness of aluminum skin 347 for mountingpurposes, it may also be pre-glued to insulation 348. Though thismounting configuration serves to protect controller assembly 305 fromadditional heat from floor plate 356, other mounting methods could beused, such as with metal brackets connected directly to the floor plate.

Much like in the previous embodiment, duct 330 extends across base plate320, thereby forming a channel 350 to direct air toward and around orthrough it. The duct 330 provides a flange along its sides and rear formounting to aluminum skin 347 through a plurality of duct mounting holes336, such as with self-tapping screws which would allow for easy removalof duct 330 as needed. Instead of fitting into a base plate groove, duct330 is attached to the sides and rear of base plate 320 using aperimeter seal 338. In this manner, the entire duct 330 can be removedfrom vehicle 300 without detaching any portion of controller assembly305. Removal of duct 330 may be desired in cases where utility vehicle300 is to be operated without mowing deck 380, as explained furtherbelow. The perimeter seal 338 serves to reduce the amount of air thatwould otherwise escape from channel 350 around controller assembly 305.In alternative embodiments, the duct may extend over entire controllerassembly 305 to include controller housing 310. This may bring more airacross controller housing 310, but complicates connection of the wiringharnesses to connector 314 and terminal block 316, and might have theadverse effect of stifling the air around controller assembly 310 inperiods when utility vehicle 300 is operating but not moving forward.

As shown in FIG. 9, the forward end of duct 330 opens across its entirewidth to form a scoop for collecting air into channel 350 as vehicle 300moves forward. Once collected, air is guided around the outside of baseplate 320 or through one of its air passages 325. As the air movesrearward, duct 330 comes together to form a relatively narrow exhaustport through which air is directed. Connected to the exhaust port ofduct 330 is a flexible hose 343 having two ends. The first end of hose343 is clamped over the exhaust port of duct 330 while the second end isclamped over the receiving end of a vacuum attachment 360, which is inturn affixed to deck 380 and/or an interior wall 362 along the rear ofmowing deck 380. The flexible hose 343 is ideally formed of rubber. Itmust be durable enough to subsist in the harsh environment below vehicleframe 354, but flexible enough to allow for relative movement that willoccur between mowing deck 380 and frame 354. Such movement is inevitableand, though no connection means are shown in FIG. 9, chains or otherlinkages are used to suspend mowing deck 380 in a manner so as to allowsuch movement.

The vacuum attachment 360 referred to above operates to direct airflowmuch like duct 330. Ideally, it is a molded plastic component having aflange for mating to interior wall 362 of mowing deck 380, such as witha plurality of rivets. In alternative embodiments, vacuum attachment 360could be mounted directly to the rear of mowing deck 380, alleviatingthe need for interior wall 362. However, it is better protected whenmounted to interior wall 362 as shown in FIGS. 8 and 9. In addition,interior wall 362 is formed so as to place passage exit opening 351 lowto the ground and close to blade 375 to improve the suction of airthrough channel 350. As mentioned above, the rotation of blades 375functions to create a low pressure zone which draws air up from undermowing deck 380, where it is then rotated by blades 375 and expelledthrough a discharge chute 381. By placing the exit point of channel 350at the bottom of mowing deck 380 below rotating blade 375, the bladeaction will tend to pull air through the exit of channel 350, extendingthe low pressure zone into channel 350. Thus, it will be understood thatthe embodiment illustrated in FIGS. 8-10 is intended to not only ram airinto the scoop at the opening of duct 330, but also to draw air throughchannel 350 from its exit at the exit point of vacuum attachment 360.

By increasing the flow rate and volume of ambient air across controllerassembly 305 through forced entry of air at the entrance of duct 330 andsuction of air through vacuum connection 360 at the exit of channel 350,duct 330, hose 343 and vacuum attachment 360 work together to accelerateconvection cooling of controller assembly 305. While the specificgeometries of duct 330, hose 343, vacuum attachment 360 and interiorwall 362 may vary, it is important that they join to form airtightconnections so as to improve the conditions for vacuum suction throughchannel 350.

The rate and volume of airflow through channel 350 may be furtherincreased, as needed, through use of one or more optional fans mountedin a variety of locations along channel 350. A fan mounted forward ofcontroller assembly 305 would serve to blow air directly toward andaround or through base plate 320, thus improving the ram air function ofthe scoop. However, such a fan would have limited use for drawing airinto channel 350 as duct 330 is relatively wide at that point.Alternatively, a fan mounted aft of the controller where duct 330narrows would serve to draw air into the passage in a pump-like fashion.However it would be unable to send air toward base plate 320 from thisposition. Maximum fan usage would thus incorporate fans both fore andaft of base plate 320 so as to improve both ram and suction functions ofthe design.

Though the one or more fans could continuously operate, ideally theywould be operated as needed by the very controller assembly 305 they areprovided to cool. Each controller assembly 305 is typically equippedwith a sensor to assess its own internal temperature. As thistemperature climbs above a pre-designated point, controller assembly 305could direct the fan(s) to switch on so as to increase airflow acrosscontroller assembly 305. Once the internal temperature is sufficientlyreduced, controller assembly 305 would direct the fan(s) to shut off.Alternatively, the operation of the fan(s) could be triggered by theambient air temperature.

While additional cooling may, thus, be provided for a controllerassembly 305 attached to vehicle frame 354 and capable of powering bothauxiliary motor(s) 376 and drive motor(s) 377, it will be noted thatsome measure of additional cooling is reliant on the operation ofauxiliary motor(s) 376 and associated auxiliary equipment (e.g., blades375). In the illustrated embodiment, should an operator wish to detachmowing deck 380 and associated auxiliary motor(s) 376 from vehicle 300for certain activities, the operator would have to decouple hose 343from duct 330, thereby losing the vacuum effect of the blades. However,the air scoop and optional fan(s) could still operate to increaseairflow across base plate 320 in the absence of mowing deck 380. Asdiscussed above, however, there may be activities wherein vehicle 300 isto operate in a stationary position for long periods of time. In suchcases, it may actually be most efficient to completely remove duct 320as well.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof

We claim:
 1. A utility vehicle comprising: a mowing deck having an uppersurface and perimeter edges extending downward from the upper surface;an electric motor positioned above the upper surface of the mowing deck;a shaft rotated by the electric motor, the shaft extending through afirst opening in the upper surface of the mowing deck; a controller forcontrolling the electric motor; a second opening in the upper surface ofthe mowing deck, the second opening spaced apart from the first openingand defining an entrance into a duct that leads to the controller; and acutting blade disposed beneath the upper surface of the mowing deck androtated by the shaft to generate an airflow by pulling ambient air upfrom under the perimeter edges of the mowing deck and pushing theairflow through the second opening and into the entrance of the ductsuch that the airflow is directed toward the controller.
 2. The utilityvehicle of claim 1, wherein the controller comprises a heat sink mountedto the upper surface of the mowing deck.
 3. The utility vehicle of claim2, wherein the heat sink is mounted over a third opening in the uppersurface of the mowing deck spaced apart from the first opening and thesecond opening.
 4. The utility vehicle of claim 2, wherein the heat sinkhas at least one internal air passage that forms a portion of the duct.5. The utility vehicle of claim 4, wherein the controller furthercomprises a plurality of heat dissipating fins extending away from thecontroller, said fins positioned so as to be external to the duct. 6.The utility vehicle of claim 1, wherein the duct is mounted on the uppersurface of the mowing deck and extends horizontally along said uppersurface to direct air perpendicularly away from the shaft.
 7. Theutility vehicle of claim 1, further comprising a filter positioned toprevent grass or other debris from passing through the duct.
 8. Theutility vehicle of claim 1, wherein the duct passes through a portion ofthe controller.
 9. The utility vehicle of claim 1, wherein thecontroller is exposed to ambient air external to the duct as well as theairflow passing through the duct.
 10. A system for cooling a controllerused to control an electric motor on a utility vehicle, the systemcomprising: a mowing deck having an upper surface and perimeter edgesextending downward from the upper surface; a cutting blade disposedbeneath the upper surface of the mowing deck, the cutting blade rotatedby a shaft that passes through a first hole in the upper surface, thecutting blade thereby generating an airflow by pulling ambient air upfrom under the perimeter edges of the mowing deck; a controllerpositioned above the upper surface of the mowing deck; and a second holein the upper surface of the mowing deck spaced apart from the firsthole, the second hole forming an opening to a duct that extends towardthe controller; wherein at least a portion of the airflow generated bythe cutting blade exits through the second hole and into the duct suchthe airflow is directed toward the controller.
 11. The system of claim10, wherein the controller forms a portion of the duct.
 12. The systemof claim 11, wherein the controller comprises a heat sink mounted to theupper surface of the mowing deck, and wherein the duct channels theportion of the airflow through the heat sink.
 13. The system of claim12, wherein the heat sink partially extends through a third hole in theupper surface of the mowing deck.
 14. The system of claim 10, whereinthe duct extends horizontally along the upper surface of the mowing deckand encapsulates a portion of the controller.
 15. The system of claim14, wherein the controller comprises a terminal block that is externalto the duct.
 16. The system of claim 10, further comprising a filter toremove grass and debris from the airflow prior to the airflow reachingthe controller.
 17. A lawn tractor comprising: a mowing deck having anupper surface and perimeter edges extending downward from the uppersurface; a cutting blade having a center connected to a drive shaft andat least two blade ends, the cutting blade rotatably suspended from thedrive shaft below the upper surface of the mowing deck such thatrotation of the cutting blade generates an airflow by pulling ambientair up from under the perimeter edges of the mowing deck; a controllermounted on the upper surface of the mowing deck, the controller used tocontrol operations of the lawn tractor; and a duct connecting thecontroller to a cutaway in the upper surface of the mowing deckpositioned away from the drive shaft through which a portion of theairflow generated by the cutting blade passes such that the airflow isdirected into contact with the controller.
 18. The lawn tractor of claim17, further comprising a filter positioned to cleanse the portion ofairflow of debris therein prior to the portion of the airflow contactingthe controller, and wherein the filter comprises a handle for use inremoving and cleaning the filter.
 19. The lawn tractor of claim 17,wherein the controller comprises a heat sink having at least oneinternal passageway through which the portion of airflow is channeled.20. The lawn tractor of claim 17, wherein a portion of the controller iswithin the duct and a portion of the controller extends outside of theduct.